Everyone who's ever taken a Neuroscience class in college remembers the strange case of H.M.
H.M. suffered from epilepsy. Back in 1953, his brain was operated on - some large chunks (the hippocampi) were removed. Epilepsy was gone. So was his memory.
He could remember his life before surgery, but could not form any new memories. More specifically, he could not remember any new events ('declarative memory'), things that happened to him. Whatever he experienced years, months, weeks, days, hours, even minutes before, was forever lost. Every moment was a fresh moment. Every day a new beginning.
But there were things he could remember - new skills (
'episodic procedural memory'). If he practiced something one day, he would be better at it the next day even though he could not remember he ever did it before. His brain could remember those subconscious new memories.
Of course, he was studied and studied all his life. A lot of what we now know about memory, we learned from studies on H.M.
H.M. died this Tuesday at the age of 82. His real name was revealed after his death: Henry Gustav Molaison. When we talk about "heroes of science" we usually think about scientists. But in cases like Henry Gustav Molaison, the real scientific hero was a subject.
In your fourth paragraph, I think you mean 'procedural memory'.
Yes, I think you do mean procedural memory - Corkin showed that H.M. retained the ability to acquire simple new motor skills. Episodoc memory, also known as autobiographical memory, refers to the memory of life events.
Also, the surgery left H.M. with quite severe retrograde amnesia - he could remember nothing that happened in the ~10 years prior to the operation.
H.M. PEACE TO YOU.....